1. Field of the Invention
The present invention relates to a cooking utensil, and particularly, to a cooking utensil having a double-layered wall structure which preserves heat entrapped during cooking.
2. Description of the Related Art
Various types of cooking utensil are known and used in a kitchen. Such cooking utensil is made of one or more layers of stainless steel and has a single-layered bottom. The single-layered bottom is good for directly transmitting heat to the food contained in the utensil, but also causes burning of the food when carefully not attended to.
To solve the above problems, a cooking utensil having a double-layered structure has been proposed for preventing burnt food and to improve food flavor. One of such ideas is:
published in Korean Utility Laid-Open Publication No. 85-7307 which teaches that paraffin is injected between a space provided by a double-layered structure and an air-hole is established thereon.
Moreover, a pot of a double-layered structure and a pot having a double-layered structure into which a working fluid is injected are taught by Japanese Laid-Open Publication No. 56-169825.
Instead of charging the space with paraffin, a structure into which a fluid of heat-medium is injected and sealed is disclosed in Korean Laid-Open Publication No. 97-4035.
In such pots having the above-mentioned structures of the related arts, the gaps between the double-layered structure are filled with heat media to provide even-heat distribution and to save heat energy. Unfortunately, the structures of the related arts are filled with the heat medium substances and have to be sealed to prevent the substances from leaking out, resulting in the difficulties in manufacturing the cookware.
Accordingly, the present invention is directed to a cooking utensil that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
The object of the present invention is to provide a cooking utensil having a double-layered structure which provide even heat distribution and preserves heat for a longer period of time.
Additional features and advantages of the invention will be set forth in the description which follows and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a cooking utensil comprises an outer shell having an opening and a first flange; an inner shell having a second flange and being disposed inside the outer shell through the opening, forming a wall space between the outer and inner shells, wherein the wall space is formed substantially along the height of the inner shell and at least partially contains air; and a first heat conductive plate being in contact with both an inner bottom surface of the outer shell and an outer bottom surface of the inner shell to allow even distribution of heat through out the bottom surface of the inner shell, wherein the first and the second flanges of the outer and inner shells are curled at about 360 degree angle and at least four times to form a rolled joint to hermetically seal the wall space.
According to one aspect of the present invention, the wall space between the outer and inner shells contains ambient air. Alternatively, the wall space defined by the outer and inner shells contains a heat conduction medium, such as silicon oil.
According to another aspect of the present invention, a second heat conduction plate is affixed to and in contact with an outer bottom surface of the outer shell. In addition, a support cover is configured to fit in surrounding relation to the second heat conduction plate. An inner lid that fits over a flange of the inner shell covers an opening defined by the inner shell. The inner lid comprises a disk having a diameter sufficiently large to cover the opening of the inner shell; and a ring coupled to the disk and circumferentially covering outer edges of the disk. The disk is made of one selected from the group of tempered glass, stainless steel, aluminum and aluminum alloy. A cover that fits over a flange of the inner shell and the lid substantially covers an opening defined by the inner shell. The cover and the lid define an air gap space therebetween for trapping heat.
When heat conducting medium, such as silicon oil is contained in the wall space defined by vertical cylindrical walls of the outer and inner shells, the amount of silicon oil stored in the wall space is approximately 55 to 75%, and more preferably about 65%, by volume.
According to another aspect of the present invention, the cooking utensil further comprises a guard ring disposed in a lower proximity of the wall space around a circumference of the first heat conduction plate. Preferably, the guard ring has an L-shaped cross section. Alternatively, the guard ring has a U-shaped cross section.
According to another embodiment of the present invention, a cooking utensil comprises an outer shell having an opening and a first flange; an inner shell having a second flange and being disposed inside the outer shell through the opening, forming a wall space between the outer and inner shells, wherein the wall space is formed substantially along the height of the inner shell and at least partially contains air, wherein an inner bottom surface of the outer shell and an outer bottom surface of the inner shell are affixed to each other to allow even distribution of heat through out the bottom surface of the inner shell; and a heat conduction plate affixed to and in contact with an outer bottom surface of the outer shell, wherein the first and the second flanges of the outer and inner shells are curled at least four times to form a rolled joint to hermetically seal the wall space.
A method of manufacturing a cooking utensil having outer and inner shells forming wall and bottom spaces between the outer and inner shells comprises the steps of placing upright the outer shell on a concaved mold, the outer shell having a flange; placing a predetermined amount of the heat conductive medium into a space defined by the outer shell placed on the first mold; placing upright the inner shell in the outer shell so that the heat conductive medium at least partially surrounds the inner shell, the inner shell having a flange placed substantially parallel to the flange of the outer shell, wherein a convexed mold is placed in the inner shell to firmly hold the inner shell with respect to the outer shell; forming a rolled joint by curling together the flanges of the outer and inner shells at least four times to prevent the heat conductive medium from being discharged from the space even when the cooking utensil is exposed to heat, wherein the curling of the flanges of the outer and inner shells is carried out by placing at least one curling roller against the flanges while rotating the outer and inner shells with respect to the curling roller;
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.